Detachable skateboard assembly

ABSTRACT

The detachable skateboard assembly includes a base part configured for detachable attachment to a board and an upper part configured for detachable attachment to the base part. The upper part is coupled to the base part in such a way that they can pivot relative to each other about a first pivoting axis. The detachable skateboard assembly further includes a wheel unit configured for attachment to the upper part and an elastomeric element arranged between the base part and the upper part such that the elastomeric element is compressed by the pivoting movement between the upper part and the base part. The elastomer element exerts a force tending to make the upper part and base part to recover a neutral position corresponding to the rectilinear displacement of the skateboard.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of European patent application no. 22382481.4, filed on May 18, 2022, the disclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to a front wheel truck for a skateboard for the purpose of improving its maneuverability to convert it into a surfskate and more particularly to a front wheel truck assembly detachably mounted on a skateboard for the purpose of improving its maneuverability to convert it into a surfskate

BACKGROUND

A traditional skateboard consists basically of a board, usually made of wood, to which four wheels are attached in pairs and which is used to practice the sport called skateboarding. The wheels are grouped in two units of two wheels each whose axle is attached with a flexible stem slightly inclined in relation to the board, which allows to make turns by tilting the board to one side or the other.

U.S. Pat. No. 6,056,302 describes an example of a wheel unit for a traditional skateboard. As can be seen in the figures, the unit consists of a base or mounting plate attached to the underside of the board and connected to the wheel axle by means of a shank or kingpin passing through a couple of bushings. This configuration allows a slight inclination of the wheels in relation to the board when the user leans on one or the other side of the board, allowing smooth turns in the direction of travel.

Recently, a new type of skateboard called “surfskate” has appeared. The difference between a traditional skateboard and a surfskate lies primarily in the type of front wheel unit used. The front wheel unit of a surfskate is configured to allow much greater maneuverability than with a traditional skateboard. For that purpose, the surfskate comprises a centering spring that exerts an action on the wheels to return them to their neutral position. A surfskate behaves very differently from a conventional skateboard, allowing the user to propel himself simply by performing oscillatory hip movements similar to those performed in surfing.

U.S. Pat. No. 6,793,224-B2 shows an example of a wheel unit for a surfskate. This unit comprises a base plate attachable to the underside of a board and an arm or pivoting member attached to the base plate such that the arm can rotate relative to the base about a first axis. A hanger having a pair of wheels mounted at opposite ends is attached to said arm and is rotatable relative thereto about a second axis. A compression spring connected between the base plate and the arm limits the rotational movement of the arm and returns it towards a central position aligned with the direction of the moving surfskate.

Although the use of this type of wheel truck greatly increases the maneuverability of a surfskate over that of a traditional skateboard, its turning capability is still somewhat insufficient. In addition, the use of a spring, as well as the various moving parts that compose the spring system, greatly limits the life of this type of wheel truck and makes it difficult to maintain and repair.

SUMMARY

A first aspect of the disclosure relates to a detachable assembly configured for attachment to a board of a traditional skateboard so as to provide it with much greater turning ability and maneuverability (to convert it into a surfskate).

The detachable skateboard assembly of the disclosure comprising:

-   -   a base part configured for detachable attachment to a board,     -   an upper part configured for detachable attachment to the base         part, the upper part being coupled to the base part in such a         way that they can pivot relative to each other about a first         pivoting axis A1,     -   a wheel unit configured for attachment to the upper part,         -   an elastomeric element arranged between the base part and             the upper part such that the elastomeric element is             compressed by the pivoting movement between the upper part             and the base part, the elastomer element exerting a force             tending to make them recover a neutral position             corresponding to the rectilinear displacement of the             skateboard.

The term “elastomeric element” as used herein refers to an element comprising, substantially consisting of (i.e. wherein the weight of the elastomeric material is greater than 90%, 95%, 96%, 97%, 98% or 99%) or consisting of a material comprising which consists of at least one elastomer. Said elastomer may be a natural elastomer (e.g. natural rubber) and/or at least one a synthetic elastomer. Said elastomers may be unsaturated (unsaturated rubbers) or saturated (saturated rubbers). Additionally, synthetic elastomers may be cured or cross-linked or, alternatively, they may be thermoplastic (i.e., thermoplastic elastomers or TPE, also known as thermoplastic rubbers). In a particular embodiment, the elastomeric element may comprise, substantially consist of, or consist of a material which consists of a plurality of elastomers.

Examples of preferred elastomers include, but are not limited to, natural rubber (NR), butyl rubber (i.e. copolymer of isobutylene with isoprene), copolymers of isobutylene and para-alkylstyrene, polyisoprene, polybutadiene (cis or trans), ethylene-propylene rubber (EPR), ethylene-propylene-diene monomer rubber (EPDM), silicone elastomers, halobutyl rubber (i.e. copolymer of halogenated isobutylene and isoprene, e.g. bromobutyl rubber (BIIR) or chlorobutyl rubber (CIIR)), polyurethane (typically also referred to as “urethane”), nitriles, styrenic block copolymer rubber (including SEBS, SI, SIS, SB (also referred to as SBR), SBS, SIBS and the like, wherein S=styrene, EB=random ethylene+butene, I=isoprene, and B=butadiene), halogenated copolymers of isobutylene and para-alkylstyrene, butadiene-acrylonitrile copolymers, alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber, polychloroprene rubber (CR, also known as chloroprene or chlorobutadiene rubber, and commercially available, for example, under trade name Neoprene®), and any combination thereof, such as, for example, elastomeric composites based on natural rubber and butadiene rubber (NR/BR); elastomeric composites based on natural rubber, butadiene rubber and styrene-butadiene rubber (NR/BR/SBR).

In an embodiment, the elastomer is selected from the group consisting of natural rubber (NR), butyl rubber (i.e. copolymer of isobutylene with isoprene), copolymers of isobutylene and para-alkylstyrene, polyisoprene, polybutadiene (cis or trans), ethylene-propylene rubber (EPR), ethylene-propylene-diene monomer rubber (EPDM), silicone elastomers, polyurethane (typically also referred to as “urethane”), nitriles, styrenic block copolymer rubber (including SEBS, SI, SIS, SB (also referred to as SBR), SBS, SIBS and the like, wherein S=styrene, EB=random ethylene+butene, I=isoprene, and B=butadiene), butadiene-acrylonitrile copolymers and alkyl acrylate rubber.

In a particular embodiment, the elastomer is selected from the group consisting of natural rubber (NR), butyl rubber (i.e. copolymer of isobutylene with isoprene), polyisoprene, polybutadiene (cis or trans), ethylene-propylene rubber (EPR), ethylene-propylene-diene monomer rubber (EPDM), polyurethane (typically also referred to as “urethane”), styrenic block copolymer rubber (including SEBS, SI, SIS, SB (also referred to as SBR), SBS, SIBS and the like, wherein S=styrene, EB=random ethylene+butene, I=isoprene, and B=butadiene) and alkyl acrylate rubber.

In still another particular embodiment, the elastomer is selected from the group consisting of natural rubber (NR), butyl rubber (i.e. copolymer of isobutylene with isoprene), polyisoprene, polybutadiene (cis or trans), polyurethane (typically also referred to as “urethane”), styrenic block copolymer rubber (including SEBS, SI, SIS, SB (also referred to as SBR), SBS, SIBS and the like, wherein S=styrene, EB=random ethylene+butene, I=isoprene, and B=butadiene) and alkyl acrylate rubber.

In another embodiment, the elastomer is selected from the group consisting of natural rubber (NR), butyl rubber (i.e. copolymer of isobutylene with isoprene), polyisoprene, polybutadiene (cis or trans) and polyurethane (typically also referred to as “urethane”). The elastomer may be particularly selected from the group consisting of polyisoprene, polybutadiene (cis or trans) and polyurethane (typically also referred to as “urethane”), more particularly, the elastomer may be polyurethane, still more particularly, cast polyurethane.

In some embodiments, the elastomeric material comprises, essentially consists of (i.e. wherein the weight of the elastomeric material is greater than 90%, 95%, 96%, 97%, 98% or 99%), or consists of a material which consists of at least one polyurethane elastomer, preferably polyurethane with a Shore hardness in the range of 60 to 100, in particular, polyurethane with a Shore hardness in the range of 70 to 90, or in the range of 75 to 95, or in the range of 80 to 100, or in the range of 60 to 90, and more preferably polyurethane with a Shore hardness A in the range of 60 to 100, in particular, polyurethane with a Shore hardness A in the range of 70 to 90, or in the range of 75 to 95, or in the range of 80 to 100, or in the range of 60 to 90. Shore hardness A is typically measured according to standard DIN 53505.

It will become apparent that the Shore hardness of the polyurethane(s) employed in the elastomeric material may be tailored by modifying the chemical properties of the polymer(s). In particular, such tailoring may depend on the choice of starting materials originally employed for synthetizing the polyurethane polymer(s), such as the polyisocyanate prepolymer and the curative composition which may typically comprise a polyol, a polymerization catalyst and a chain extender. Depending on the nature of the polyisocyanate prepolymer, the polyol, the chain extender and even the catalyst of choice, it is possible to modify the length of the resulting polyurethane, as well as its Shore hardness, thus being able to modify the behavior of the surfskate of the present disclosure.

In an embodiment, the polyurethane elastomer may be a 4,4′-diphenylmethane diisocyanate (MDI) based polyurethane, a toluene diisocyanate (TDI) based polyurethane, an isophorone diisocyanate (IPDI) based polyurethane or a methylene-bis[(4-cyclohexyl)-diisocyanate] (CHDI) based polyurethane. In another embodiment, the polyurethane elastomer may be a 4,4′-diphenylmethane diisocyanate (MDI) based cast polyurethane, a toluene diisocyanate (TDI) based cast polyurethane, an isophorone diisocyanate (IPDI) based cast polyurethane or a methylene-bis[(4-cyclohexyl)-diisocyanate] (CHDI) based cast polyurethane.

In some embodiments, the elastomeric material comprises, essentially consists of (i.e. wherein the weight of the elastomeric material is greater than 90%, 95%, 96%, 97%, 98% or 99%), or consists of a material which consists of a cast polyurethane elastomer (i.e. cast polyurethane) obtained by reacting a polyisocyanate prepolymer with a curative composition, wherein the cast polyurethane elastomer may have a Shore hardness in the range of 60 to 100, in the range of 70 to 90, in the range of 75 to 95, in the range of 80 to 100, or in the range of 60 to 90 and, more preferably, the cast polyurethane elastomer may have a Shore hardness A in the range of 60 to 100, in the range of 70 to 90, in the range of 75 to 95, in the range of 80 to 100, or in the range of 60 to 90.

In some embodiments, the cast polyurethane elastomer may be obtained by reacting a polyisocyanate prepolymer with a curative composition, wherein said curative composition comprises a polymerization catalyst and, optionally, a polyol selected from polyether polyols and polyester polyols, and optionally a chain extender. As will become apparent, the ratio of those different components, which together undergo a polymerization reaction to provide polyurethane, will typically depend on the final properties of the polyurethane elastomer which are required for subsequent applications. In some embodiment, the cast polyurethane elastomer may be obtained by reacting 100-1000 parts per weight of a polyisocyanate prepolymer with a curative composition, wherein said curative composition comprises 0-150 parts per weight of a polyol selected from polyether polyols and polyester polyols, 0.5-1 parts per weight of a polymerization catalyst, and 0-100 parts per weight of a chain extender. In another embodiment, the cast polyurethane elastomer may be obtained by reacting 100-1000 parts per weight of a polyisocyanate prepolymer with a curative composition, wherein said curative composition comprises 0-150 parts per weight of a polyol selected from polyether polyols and polyester polyols, 0.5-1 parts per weight of a polymerization catalyst, and 10-100 parts per weight of a chain extender. In still another embodiment, the cast polyurethane elastomer may be obtained by reacting 100-1000 parts per weight of a polyisocyanate prepolymer with a curative composition, wherein said curative composition comprises between higher than 0 and 150 parts per weight of a polyol selected from polyether polyols and polyester polyols, 0.5-1 parts per weight of a polymerization catalyst, and 10-100 parts per weight of a chain extender. In still even another embodiment, the cast polyurethane elastomer may be obtained by reacting 100-1000 parts per weight of a polyisocyanate prepolymer with a curative composition, wherein said curative composition comprises 50-150 parts per weight of a polyol selected from polyether polyols and polyester polyols, 0.5-1 parts per weight of a polymerization catalyst, and 10-100 parts per weight of a chain extender.

The polyisocyanate prepolymer may be a 4,4′-diphenylmethane diisocyanate (MDI) based polyisocyanate prepolymer, a toluene diisocyanate (TDI) based polyisocyanate prepolymer, an isophorone diisocyanate (IPDI) based polyisocyanate prepolymer or a methylene-bis[(4-cyclohexyl)-diisocyanate] (CHDI) based polyisocyanate prepolymer. In a preferred embodiment, the polyisocyanate prepolymer is selected from the group consisting of a 4,4′-diphenylmethane diisocyanate (MDI) based polyisocyanate prepolymer, a toluene diisocyanate (TDI) based polyisocyanate prepolymer, and any combination thereof.

The polyol in the curative composition may preferably be a polyether polyol, which may be selected from the group consisting of polyethylene glycol (PEG), polytetramethylene ether glycol (PTMEG), polytrimethylene glycol (PTriMEG), polypropylene glycol (PPG), polybutylene ether glycol, polytetrahydrofuran (PTHF) and copolyether of ethylene oxide and propylene oxide. More preferably, the polyol in the curative composition is preferably a polyether polyol selected from the group consisting of polyethylene glycol (PEG), polytetramethylene ether glycol (PTMEG), polytrimethylene glycol (PTriMEG), polypropylene glycol (PPG) and polytetrahydrofuran (PTHF). Still more preferably, the polyol in the curative composition is polytetramethylene ether glycol (PTMEG), polytrimethylene glycol (PTriMEG) or polytetrahydrofuran (PTHF) and, still even more preferably, the polyol in the curative composition is polytetramethylene ether glycol (PTMEG) or polytrimethylene glycol (PTriMEG). The polyol in the curative composition may preferably be a polyester.

Examples of some types of optional chain extenders include 1,4-butanediol (BDO), diethylene glycol, trimethylol propane and hydroquinone di(beta hydroxyethyl ether), wherein the chain extender may preferably be 1,4-butanediol (BDO). The polymerization catalyst may include tertiary amine catalysts or suitable organometallic catalysts, such as tin, zirconium and bismuth catalysts.

In some embodiments, the elastomeric material comprises, essentially consists of (i.e. wherein the weight of the elastomeric material is greater than 90%, 95%, 96%, 97%, 98% or 99%), or consists of a material which consists of at least one polyurethane elastomer obtained by reacting a polyisocyanate prepolymer with a curative composition, wherein said curative composition comprises: a polyether polyol; a polyisocyanate prepolymer which is selected from the group consisting of a 4,4′-diphenylmethane diisocyanate (MDI) based polyisocyanate prepolymer, a toluene diisocyanate (TDI) based polyisocyanate prepolymer, and any combination thereof; a polymerization catalyst; and a chain extender which may preferably be 1,4-butanediol.

In still another embodiment, the elastomeric material comprises, essentially consists of (i.e. wherein the weight of the elastomeric material is greater than 90%, 95%, 96%, 97%, 98% or 99%), or consists of a material which consists of at least one polyurethane elastomer obtained by reacting a polyisocyanate prepolymer with a curative composition, wherein said curative composition comprises: a polyether polyol selected from the group consisting of polyethylene glycol (PEG), polytetramethylene ether glycol (PTMEG), polytrimethylene glycol (PTriMEG), polypropylene glycol (PPG), polybutylene ether glycol, and copolyether of ethylene oxide and propylene oxide; a polyisocyanate prepolymer which is selected from the group consisting of a 4,4′-diphenylmethane diisocyanate (MDI) based polyisocyanate prepolymer, a toluene diisocyanate (TDI) based polyisocyanate prepolymer, and any combination thereof; a polymerization catalyst; and a chain extender which may preferably be 1,4-butanediol.

In some embodiments the wheel unit is configured for detachable attachment to the upper part. In these embodiments the wheel unit is coupled to the upper part in such a way that they can pivot relative to each other.

In some embodiments the upper part or the base part comprises a cam element configured to push upon the elastomeric element during a pivoting movement between the upper part and the base part causing an elastic compression of the elastomeric element. The elastomeric element is preferably placed and retained between the base part and the upper part, for example at least partially housed in the base part whilst the cam element is provided in the upper part. Alternatively, the elastomeric element can be at least partially housed in the upper part whilst the cam element is provided in the base part

In some embodiments the base part or the upper part comprises a housing configured to accommodate the elastomeric element leaving a clearance space, the cam element being configured to be fitted in the clearance space.

In some embodiments the elastomeric element comprises at least one edge where the cam pushes during the pivoting movement between the base part and the upper part. The edge can be any kind of end, hole or recess defining a surface with a dimension and orientation adapted to support the pushing force exerted by the cam and produce the compression of the elastomeric element.

In the present disclosure the terms clearance space or recces means that the housing is not completely occupied by the elastomeric element (and other auxiliary parts) leaving a free space for housing the cam element. The elastomeric element can be partially or completely housed in the housing of the base part.

In some preferred embodiments the base part comprises a housing configured to accommodate the elastomeric element and to leave a clearance space or recess defined between the housing and two edges of the elastomeric element. In this embodiment the upper part comprises the cam element and the cam element is configured to be fitted in the recess between the two edges of the elastomeric element.

In some embodiments the elastomeric element comprises a plurality of pieces and wherein, at least two of these pieces comprise a first edge and an opposite second edge, the at least two pieces being placed in the housing such that the second edges of both pieces keep facing each other leaving a clearance space.

In some embodiments the base part, the elastomeric element or both comprise retention means to block the movement of the elastomeric element during the relative pivoting movement between the upper part and the base part (whilst permitting the elastic compression of the elastomeric element).

In some embodiments the first edge of the at least two pieces of the elastomeric element is placed in the housing facing the retention means such that the pivoting movement between the upper part and the base part causes the pushing of the cam element against one of the second edges and the compression of the elastomeric piece pushing one of the first edges upon the retention means.

In some embodiments the elastomeric element can comprise one single piece. In this embodiment the single elastomeric piece comprises two second edges and is placed in the housing such that the second edges keep facing each other leaving a clearance space or recess. The single elastomeric piece or the housing or both comprise retention means such that the pivoting movement between the upper part and the base part causes the pushing of the cam element against one of the second edges and the compression of the elastomeric piece pushing upon the retention means.

In other embodiments the elastomeric element can comprise a plurality of pieces (i.e. more than two pieces). In this particular embodiment, it will become apparent that, under certain circumstances wherein particular hardness or bounce properties may be of interest, each piece of the plurality of pieces may comprise, substantially consist of, or consist of a material which consists of at least one elastomer, wherein the material may be the same or different for each piece, i.e. all pieces may comprise, substantially consist of, or consist of the same material; or one or more pieces may comprise, substantially consist of, or consist of a material which is different to the material of the other pieces within said plurality of pieces; or all pieces within the plurality of pieces may comprise, substantially consist of, or consist of a different material.

The base part or the upper part can comprise a rear wall extending between a lateral wall and an inner cylindrical wall thus defining the retention means.

The lateral wall of the base part or upper part can comprise vertical ribs configured to limit the friction of the elastomeric element with the lateral wall.

The inner cylindrical wall of the base part or upper part can comprise vertical ribs configured to limit the friction of the elastomeric element with the cylindrical wall.

In some embodiments the upper part can comprise a semicircular rib configured to press the elastomeric element against a bottom surface of the housing of the base part. In alternative embodiments the base part can comprise a semicircular rib configured to press the elastomeric element against a bottom surface of the housing of the upper part.

In some embodiments the detachable skateboard assembly comprises a bolt, passing the base part and the upper part such that the upper part can pivot relative to the base part around said bolt and wherein the bolt comprises a bolt head and a threaded edge, the bolt head being configured to push upon the base part and the threaded edge protruding partially outside the upper part such that a locking nut engages the threaded edge of the bolt blocking together the upper part and the base part in the direction of the first axis. In this way, to separate the base part from the upper part and remove the elastomeric element and all the internal parts of the assembly is not necessary to separate the assembly from the board or the wheel unit but simply remove the locking nut.

In some embodiments the detachable skateboard assembly comprises a lower axial bearing located between the base part and the upper part, an upper axial bearing located between the upper part and the locking nut, and a bronze bushing between the lower axial bearing and the upper axial bearing, such that the bolt extends through the base part, the lower axial bearing, the bronze bushing, the upper part, the upper axial bearing and the locking nut.

In some embodiments the housing of the base part is substantially annular shaped with an inner cylindrical wall comprising a central bore wherein the bolt passes through the base plate. In these embodiments the elastomeric element can be a substantially a toroidal single piece with a central hole such that when the elastomeric element is placed in the annular shaped housing the bolt passes through the central hole of the toroidal elastomeric element. This toroidal elastomeric element comprises a recess or hole for the cam to push upon. The elastomeric element can comprise two or more pieces placed in the annular shaped housing surrounding the central bore but leaving a clearance space or recess.

In some embodiments the upper part comprises a pedestal for the coupling to the base part and an elongated arm for the attachment of a wheel unit. The wheel unit comprises a hanger with two axle rods for the wheels and a pivot pin configured to engage a pivot cup housed in a blind hole of the elongated arm, the hanger further comprising a platform with an eyelet suitable for the attachment to the upper part by means of a kingpin and a couple of bushings, the kingpin passing through the eyelet, the bushings and a counter hole of the elongated arm of the upper part.

In alternative embodiments the upper part comprises a pedestal for the coupling to the base part and a substantially planar support base where an intermediate part can be attached. The wheel unit comprises a hanger with two axle rods for the wheels and a pivot pin configured to engage a pivot cup housed in the blind hole of the intermediate part, the hanger further comprising a platform with an eyelet suitable for the attachment to intermediate part by means of a kingpin and a couple of bushings, the kingpin passing through the eyelet, the bushings and a counter hole of the intermediate part.

In another embodiment the upper part comprises a pedestal for the coupling to the base part, a substantially vertical arm and an axle comprising two axle rods for the wheels. In this embodiment the wheel unit is a part of the upper part and cannot be detached.

The configurations of the present disclosure are advantageous in relation to the assemblies normally used in a surfskate for several reasons.

First, the assembly of the present disclosure employs an elastomeric element instead of the compression spring and thus the assembly is more compact with the use of an elastomer, and therefore simpler, more robust, easier to assemble, and less prone to failure.

In addition, the behavior of the elastomer under stress is very different from that of a compression spring, and its response changes with the chemical composition of the elastomer, for example, its hardness or its bounce, among others.

Secondly, the assembly of the present disclosure is simpler to assemble and disassemble since the assembly of the present disclosure preferably uses a single nut for the fixing of all the elements. In this way, to access to any part of the assembly is not necessary to separate it from the board or the wheel unit to which it is mounted, but simply by removing the locking nut. This makes it possible to separate the base part from the upper part and to remove all the internal parts of the assembly.

Moreover, the elastomer housed in the cavity can be changed in a simple manner, which makes it possible to modify the behavior of the surfskate. Indeed, it is sufficient to remove the fixing nut and extract the upper part to gain access to the housing where the elastomer is located, which can then be exchanged for another with a different hardness and properties. A lower hardness has a softer stress behavior curve, while a higher hardness has a more aggressive curve.

BRIEF DESCRIPTION OF THE DRAWINGS

To complete the description and in order to provide for a better understanding of the disclosure, a set of drawings is provided. Said drawings form an integral part of the description and illustrate embodiments of the disclosure, which should not be interpreted as restricting the scope of the disclosure, but just as examples of how the disclosure can be carried out.

The drawings comprise the following figures:

FIG. 1 shows an exploded perspective according to a first embodiment of the disclosure.

FIG. 2A shows a perspective view of the base part.

FIG. 2B shows a perspective view in cross section of the base part.

FIG. 3A shows a perspective view of an embodiment of the elastomeric element.

FIG. 3B shows perspective view of the base part with the elastomeric element of FIG. 3A housed therein.

FIG. 4A shows a perspective view of the upper part according to the first embodiment of the disclosure.

FIG. 4B shows a cross section view of the upper part according to the first embodiment of the disclosure.

FIG. 4C shows a bottom side view of the upper part according to the first embodiment of the disclosure.

FIG. 5 shows a perspective view of the first embodiment of the assembly of the disclosure

FIG. 6A shows a top view of the first embodiment of the assembly of the disclosure in a neutral position.

FIG. 6B shows a top view of the first embodiment of the assembly of the disclosure in a pivoted position.

FIG. 7 shows a side view of the first embodiment of the assembly of the disclosure

FIG. 8 shows a cross section view according to lines A-A in FIG. 6A.

FIG. 9 shows a cross section view according to lines B-B in FIG. 6A.

FIG. 10 shows a partially exploded perspective according to a second embodiment of the disclosure.

FIG. 11 shows a perspective view of the second embodiment of the assembly of the disclosure

FIG. 12 shows a perspective view of the base part and upper part of the second embodiment of the assembly of the disclosure

FIG. 13 shows a cross section view of the second embodiment of the disclosure.

FIG. 14 shows a partially exploded perspective according to a second embodiment of the disclosure.

FIG. 15 shows a perspective view of a third embodiment of the assembly of the disclosure.

FIG. 16 shows a cross section view of the third embodiment of the disclosure

FIG. 17 shows an exploded perspective according to the third embodiment of the disclosure.

FIG. 18 a perspective view of a skateboard with the assembly of the disclosure.

FIG. 19 shows a side view of a skateboard with the assembly of the disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded view of an exemplary detachable skateboard assembly according to a first embodiment of the present disclosure. A base part 1 is detachably attached to an upper part 2 by means of a bolt 3 such that both parts 1 and 2 can pivot relative to each other about a first pivoting axis A1. The bolt 3 extends through the base part 1, a lower axial bearing 4 located between the base piece 1 and the upper piece 2, an upper axial bearing 5 located between the upper piece 2 and a locking nut 6, and a bronze bushing 7 located between the lower axial bearing 4 and the upper axial bearing 5. The bolt 3 comprises a bolt head 8 configured to push upon the base part 1 and a threaded edge 9 protruding partially outside the upper part 2 such that the locking nut 6 engages the threaded edge 9 of the bolt blocking together the upper part 2 and the base part 1 in the direction of the first axis A1 but allowing a pivoting movement between the upper part 2 and the base part 1.

The base part 1 comprises a base plate 11 for the attachment to a board 100 by means of screws or bolts.

In this way, for having access to any part of the assembly is not necessary to detach it from the board 100 or the wheel unit to which it is mounted, but simply remove the locking nut 6. This makes it possible to separate the base part 1 from the upper part 2 and to remove all the internal parts of the assembly.

FIGS. 2A and 2B show respectively a perspective and a cross section of an embodiment of the base part 1. The base part 1 has a flat surface called base plate 11 intended to be supported on a board 100 of the skateboard for the fixing thereof to the same. To this end, countersunk screws are introduced by way of the threaded bores 12 of the base plate 11 and holes corresponding to the front part or nose of the skateboard 100. The base part 1 comprises an essentially cylindrical lateral wall 13 and an inner cylindrical wall 14 such that in-between the lateral wall 13 and the inner cylindrical wall 14 a substantially annular shaped housing 15 is defined.

The assembly of the disclosure comprises an elastomeric element 20 configured to be housed in the annular shaped housing 15. In one embodiment shown in FIGS. 3A and 3B the elastomeric element 20 consists of two pieces with a substantially arc shaped configuration. The longitudinal dimension of the housing 15 is greater than the longitudinal dimension of the elastomeric element 20 such that a recess or clearance space 151 is defined between the housing 15 and the elastomeric material 20 when the elastomeric material is housed in the housing 15 of the base part 1.

The base part 1 also comprises a rear wall 17 extending between the lateral wall 13 and the inner cylindrical wall 14 defining retention means such that the two pieces of the elastomeric element 20 placed in the annular shaped housing 15 cannot move during the pivoting movement between the upper part 2 and the base 1 as can be explained later in more detail.

As shown in FIGS. 4A, 4B, 4C, 8, 13, 14, 16 and 17 in one embodiment the upper part 2 comprises a cam element 21 configured to be fitted in the recess or clearance space 151 between the housing 15 and the elastomeric element 20 when the upper part 2 is coupled to the base part 1. The cam element 21 is configured such that during a pivoting movement between the upper part 2 and the base part 1 the cam element 21 exerts a pushing force upon the elastomeric element 20 causing an elastic compression of the elastomeric element 20.

The elastomeric element 20 comprises, in an embodiment shown in FIGS. 3A and 3B, a first piece 201 and a second piece 202, each piece 201, 202 comprising respectively a first end 211, 212 and an opposite second end 221, 222, the pieces 201, 202 being placed in the housing 15 of the base part 1 such that the first ends 211, 212 of both pieces 201, 202 keeps facing the retention means 17 of the base part 1 whilst the second ends 221, 222 face each other leaving a clearance space 151. The pivoting movement between the upper part 2 and the base part 1 causes the pushing of the cam element 21 against one of the second ends 221, 222 and the compression of the elastomeric piece 20 pushing its first end 211, 212 upon the retention means 17. The pivoting movement between the upper part 2 and the base part 1 in a first pivoting direction causes the cam element 21 to push the second end 221 of the first piece 201 of the elastomeric element 20 and the pivoting movement between the upper part 2 and the base part 1 in a second pivoting direction, opposed to the first direction, causes the cam element 21 to push the second end 222 of one of the second piece 202 of the elastomeric element 20.

As represented in FIGS. 2A and 2B the lateral wall 13 can comprise, in its inner surface, vertical ribs 131 configured to limit the friction of the elastomeric element 20 with the lateral wall 13. The inner cylindrical wall 14 can also comprise, in its outer surface, vertical ribs 141 configured to limit the friction of the elastomeric element 20 with the inner cylindrical wall 14.

The inner cylindrical wall 14 comprises an upper planar surface 142 where the lower axial bearing 4 rests and a central 16 bore wherein the bolt 3 passes through.

In the first embodiment of the disclosure, as shown in FIGS. 4A, 4B y 4C, the upper part 2 comprises a pedestal 22 for the coupling to the base part 1 and an elongated arm 23.

The pedestal 22 comprises an orifice 25 where the bronze bushing 7 fits tightly to reduce the friction between the nut 3 and the upper part 2 and a seat 26 where the upper axial bearing 5 rests.

The elongated arm 23 of the upper part 2 comprises a bling hole 24 defining a second pivoting axle A2.

FIGS. 1, 5, 6, 7, 8 and 9 show a wheel unit 40 according to the first embodiment. The wheel unit 40 comprises a hanger 41 with two axle rods 42 for the wheels and a pivot pin 43 configured to engage a pivot cup 241 housed in the blind hole 24 of the upper part 2. The hanger 41 comprises a platform 44 with an eyelet 441 suitable for the attachment to the upper part 2 by means of a kingpin 50, a nut 53, a couple of bushings 51, 52 and cups 54, 55. The kingpin 50 extends through the eyelet 441, the bushings 51, 52, the cups 54, 55 and a counter hole 231 of the elongated arm 23 of the upper part 2.

FIG. 6A shows a detail of the assembly of the disclosure in a neutral position corresponding to a rectilinear displacement of the skateboard. In this neutral position, no type of force is exerted on the longitudinal laterals of the board 100 and thus no compression is caused to the elastomeric element 20.

When a force F is exerted on the longitudinal lateral of the board 100 the upper part 2 rotates with respect to the bolt 3 while compressing the elastomeric element 20. FIG. 6B shows a detail of the assembly of the disclosure in one open position in a clockwise direction.

When the force F ceases to be exerted on the longitudinal lateral of the board 100, the elastomeric element 20 returns the accumulated energy and returns the assembly to the neutral position thereof corresponding to the rectilinear displacement. By alternating the application of force on the laterals of the board, simulating the way in which the body moves on a surfboard in order to cause it to turn towards both sides, a movement towards the front of the surfskate is produced.

In a second embodiment shown in FIGS. 10, 11, 12, 13 and 14 the upper part 2 comprises a pedestal 22 for the coupling to the base part 1 in a similar way as in the embodiment shown in FIGS. 5, 7, 8 and 9 but instead of a an elongated arm 23, in this embodiment the upper part comprises a substantially planar support base 27 where an intermediate part 61 of a wheel unit can be attached (by means of screws, bolts or the like). The intermediate part 61 comprises a bling hole 62 defining the second pivoting axle A2. The wheel unit 60 also comprises a hanger 41 with two axle rods 42 for the wheels and a pivot pin 43. In this embodiment the pivot pin is configured to engage a pivot cup 63 housed in the blind hole 62 of the intermediate part 61. The hanger 41 further comprising a platform 44 with an eyelet 441 suitable for the attachment to intermediate part 61 by means of a kingpin 50 a nut 53 and a couple of bushings 51, 52. The kingpin 50 extends through the eyelet 441, the bushings 50, 51 and a counter hole 64 of the intermediate part 61.

In this second embodiment, as shown in FIGS. 13 and 14 , similarly to the first embodiment, the base part 1 is detachably attached to an upper part 2 by means of a bolt 3 such that both base parts 1 and upper 2 can pivot relative to each other about a first pivoting axis A1. The bolt 3 extends through the base part 1, a lower axial bearing 4 located between the base piece 1 and the upper piece 2, an upper axial bearing 5 located between the upper piece 2 and a locking nut 6, and a bronze bushing 7 located between the lower axial bearing 4 and the upper axial bearing 5. The bolt 3 comprises a bolt head 8 configured to push upon the base plate 1 and the threaded edge 9 protruding partially outside the upper part 2 such that a locking nut 6 engages the threaded edge 9 of the bolt blocking together the upper part 2 and the base part 1 in the direction of the first axis A1 but allowing a pivoting movement between the upper part 2 and the base part 1. The base part 1 comprises a base plate 11 for the attachment to a board 100 by means of screws or bolts.

In a third embodiment shown in FIGS. 15, 16 and 17 the wheel unit is not detachable from the upper part 2. In fact, the upper part comprises a pedestal 23 for the coupling to the base part 2, a substantially vertical arm 28 and an axle 70 comprising two axle rods 71 where the wheels can be mounted. This is a much simple assembly but keeping all the advantages of the disclosure.

In this third embodiment, as shown in FIGS. 16 and 17 , similarly to the first and second embodiments, the base part 1 is detachably attached to an upper part 2 by means of a bolt 3 such that both parts 1 and 2 can pivot relative to each other about a first pivoting axis A1. The bolt 3 extends through the base part 1, a lower axial bearing 4 located between the base piece 1 and the upper piece 2, an upper axial bearing 5 located between the upper piece 2 and a locking nut 6, and a bronze bushing 7 located between the lower axial bearing 4 and the upper axial bearing 5. The bolt 3 comprises a bolt head 8 configured to push upon the base plate 1 and the threaded edge 9 protruding partially outside the upper part 2 such that a locking nut 6 engages the threaded edge 9 of the bolt blocking together the upper part 2 and the base part 1 in the direction of the first axis A1 but allowing a pivoting movement between the upper part 2 and the base part 1. The base part 1 comprises a base plate 11 for the attachment to a board 100 by means of screws or bolts.

FIGS. 18 and 19 respectively show a perspective view and a lateral view of a skateboard with the assembly of the disclosure mounted of the nose of the skateboard. At the tail of the skateboard a wheel unit 60 is mounted on a shim 70 to elevate the tail part so that the nose of skateboard is not elevated too much. The rear wheel unit 60 performs a similar function to that of the keel of a surfboard during the transformation of the skateboard to a surfskate.

In this text, the terms first, second, third, etc. have been used herein to describe several devices, elements or parameters, it will be understood that the devices, elements or parameters should not be limited by these terms since the terms are only used to distinguish one device, element or parameter from another. For example, the first device could as well be named second device, and the second device could be named first device without departing from the scope of this disclosure.

In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.

On the other hand, the disclosure is obviously not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the disclosure as defined in the claims. 

1. A detachable skateboard assembly comprising: a base part configured for detachable attachment to a board, an upper part configured for detachable attachment to the base part, the upper part being coupled to the base part in such a way that the upper part and the base part are configured to pivot relative to each other about a first pivoting axis, a wheel unit configured for attachment to the upper part, and an elastomeric element arranged between the base part and the upper part such that the elastomeric element is compressed by the pivoting movement between the upper part and the base part, the elastomeric element exerting a force tending to make them recover a neutral position corresponding to the rectilinear displacement of the skateboard.
 2. The detachable skateboard assembly according to claim 1, wherein the elastomeric element comprises a material which comprises at least one elastomer, wherein the elastomer is selected from the group consisting of natural rubber, butyl rubber, copolymers of isobutylene and para-alkylstyrene, polyisoprene, polybutadiene, ethylene-propylene rubber, ethylene-propylene-diene monomer rubber, silicone elastomers, polyurethane, nitriles, styrenic block copolymer rubber, butadiene-acrylonitrile copolymers and alkyl acrylate rubber; wherein the elastomer is selected from the group consisting of natural rubber, butyl rubber, polyisoprene, polybutadiene, ethylene-propylene rubber, ethylene-propylene-diene monomer rubber, polyurethane, styrenic block copolymer rubber and alkyl acrylate rubber.
 3. The detachable skateboard assembly according to claim 2, wherein the at least one elastomer is polyurethane with a Shore hardness in the range of 60 to
 100. 4. The detachable skateboard assembly according to claim 2, wherein the at least one elastomer is polyurethane, obtained by reacting a polyisocyanate prepolymer with a curative composition, wherein the curative composition comprises: a polymerization catalyst; a polyol selected from polyether polyols and polyester polyols; and a chain extender.
 5. The detachable skateboard assembly according to claim 1, wherein the upper part or the base part comprises a cam element configured to push upon the elastomeric element during the pivoting movement between the upper part and the base part causing an elastic compression of the elastomeric element.
 6. The detachable skateboard assembly according to claim wherein the base part or the upper part comprises a housing configured to accommodate the elastomeric element leaving a clearance space, the cam element being configured to be fitted in the clearance space.
 7. The detachable skateboard assembly according to claim wherein the elastomeric element comprises a plurality of pieces and wherein at least two pieces of the plurality of pieces comprise a first edge and an opposite second edge, the at least two pieces being placed in the housing such that the second edges of both pieces keeps facing each other leaving a free space defining the clearance space.
 8. The detachable skateboard assembly according to previous claim 1, wherein the base part, the elastomeric element or both comprise retention means to block the movement of the elastomeric element during the relative pivoting movement between the upper part and the base part.
 9. The detachable skateboard assembly according to claim 8, wherein the first edge of the two pieces of the elastomeric element is placed in the housing facing the retention means such that the pivoting movement between the upper part and the base part causes the pushing of the cam element against one of the second edges and the compression of the elastomeric piece pushing one of the first edges upon the retention means.
 10. The detachable skateboard assembly according to claim 1, comprising a bolt passing the base part and the upper part such that the upper part is configured to pivot relative to the base part around said bolt and wherein the bolt comprises a bolt head and a threaded edge, the bolt head being configured to push upon the base part and the threaded edge protruding partially outside the upper part such that a locking nut engages the threaded edge of the bolt blocking together the upper part and the base part in the direction of the first pivoting axis.
 11. The detachable skateboard assembly according to claim 10, comprising a lower axial bearing located between the base part and the upper part, an upper axial bearing located between the upper part and the locking nut, and a bronze bushing between the lower axial bearing and the upper axial bearing, such that the bolt extends through the base part, the lower axial bearing, the bronze bushing, the upper part, the upper axial bearing and the locking nut.
 12. The detachable skateboard assembly according to claim 1, wherein the upper part comprises a pedestal for the coupling to the base part and an elongated arm for the attachment of a wheel unit, the wheel unit comprising a hanger with two axle rods for the wheels and a pivot pin configured to engage a pivot cup housed in a blind hole of the elongated arm, the hanger further comprising a platform with an eyelet suitable for the attachment to the upper part by means of a kingpin and a couple of bushings, the kingpin passing through the eyelet, the bushings and a counter hole of the elongated arm of the upper part.
 13. The detachable skateboard assembly according to claim 1, wherein the upper part comprises a pedestal for the coupling to the base part and a substantially planar support base where an intermediate part of a wheel unit is configured to be attached and wherein the wheel unit further comprises a hanger with two axle rods for the wheels and a pivot pin configured to engage a pivot cup housed in a blind hole of the intermediate part (61), the hanger further comprising a platform with an eyelet suitable for the attachment to intermediate part by means of a kingpin and a couple of bushings, the kingpin passing through the eyelet, the bushings and a counter hole of the of the intermediate part.
 14. The detachable skateboard assembly according to claim 1, wherein the upper part comprises a pedestal for the coupling to the base part and a substantially vertical arm wherein and an axle comprising two axle rods for the wheels is attached.
 15. The skateboard comprising a detachable assembly according to claim
 1. 